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Rock-mass unloading often occurs during underground and slope engineering excavations. Here, rock-mass crack initiation and propagation during the excavation unloading progress was simulated using the extended finite element method (XFEM) in ABAQUS. Crack propagation and its influencing factors were studied and discussed after calculating the stress intensity factors at the crack tips, and by recording the crack's shape a dynamic evolution model was produced. The results show that the faster the unloading rate,the longer the crack,and the greater the crack dip angle, the easier the crack initiates. The normal stress on a crack surface decreases while shear stress increases during unloading, and that crack propagation is mainly controlled by shear stress. This is consistent with the theoretical analysis. The final shape of the modeled crack was also close to the result of the physical experiments, indicating the reliability of this study.

BACKGROUND: Unicompartmental knee osteoarthritis can be treated clinically with either total or partial knee arthroplasty. In the choice of treatment methods, a variety of factors lead to significant differences. There is little reliable evidence to guide the clinical surgical options OBJECTIVE: To compare the short-term curative effect of unicompartmental and total knee arthroplasties in the treatment of unicompartmental osteoarthritis and to explore the effects of two treatment methods on the balance function of patients. METHODS: This was a perspective trial. The patients with unicompartmental knee osteoarthritis were divided into unicompartmental knee arthroplasty group (22 cases, 23 knees) and total knee arthroplasty group (30 cases, 30 knees) based on surgical method. All patients signed the informed consents and the study was approved by the hospital ethical committee. The operation time, hospitalization time, Hospital for Special Surgery score, and the range of motion of the knee joint were compared between two groups to evaluate the early efficacy. The patients' balance function was evaluated using the Tecnobody Proprioception Test System, Timed Up and Go test, and Berg Balance Scale before and 3 months after surgery. RESULTS AND CONCLUSION: (1) Compared with the total knee arthroplasty group, the unicompartmental knee arthroplasty group had shorter operation time and hospitalization time (P < 0.001 ). (2) At 3 months after surgery, there was no significant difference in the Hospital for Special Surgery score, range of motion of the knee joint, Timed Up and Go test or Berg Balance Scale score between two groups (P > 0.05). The Tecnobody Proprioception Test System scores at 3 months after surgery in the unicompartmental knee arthroplasty group were significantly higher than those in the total knee arthroplasty group (P < 0.001 ). (3) These results indicate that both unicompartmental and total knee arthroplasties have satisfactory short-term results in the treatment of unicompartmental knee osteoarthritis. Unicompartmental knee arthroplasty is superior to total knee arthroplasty in terms of operation time, hospitalization time, and balance function recovery. [ABSTRACT FROM AUTHOR]